1. Field of Invention
This invention finds use in the field of polymer material blends for use in products manufactured for the electrical utility market. In particular, this invention relates to a cross-linked polyolefin blend having characteristics compatible with the requirements of electrical utility products, upon molding.
2. Background
Thermoplastic materials have been used in the electrical industry for many years such as in 15 kV pin type polymeric insulator, introduced in 1969. Since that time additional insulators have been added, such as in the 25 kV and 35 kV categories. Vise-tops insulators, which include an integral cable clamp were added to each voltage category some time later. The thermoplastic material presently used to produce the insulators is a high-density polyethylene (HDPE). Stabilizers are incorporated in optimum percentages to maintain the original electrical and mechanical properties for the lifetime of the product as it is exposed to the environment, in particular ultraviolet (UV) light, and electrical stress from the energized cables and system. The stabilizers also impart other properties such as track and UV resistance. The final blended material possesses electrical and mechanical characteristics sufficient for the intended application.
However, the typical HDPE material has a temperature limitation at/below 120° C. A typical polyurethane insulator is used in overhead electrical applications to isolate electrical cables from ground. The insulator is required to meet all performance criteria of the applicable ANSI C 29.1 specification. It also is required to meet requirements of tracking and UV Resistance. Utilities have been required to carry heavier current loads resulting in hotter conductors. Current materials such as HDPE cannot meet such conditions.
Therefore, under present electrical transmission requirements, there exists a need for a material that can withstand conductor temperatures in excess of 120° C. without weakening or loss of structure and performance.